Glow discharge tubes



Feb. 6, 1962 G. J. M. AHSMANN 3,020,436

GLOW DISCHARGE TUBES Filed May 11, 1960 INVENTOR. 6.J.M. AHSMANN AGENT United States Patent 3,020,436 GLOW DISCHARGE TUBES Gerartlus Josephus Marie Ahsmann, Eindhoven, Netherlands, assignor to North American Philips Company,

Inc, New York, N.Y., a corporation of Delaware Filed May 11, 1960, Ser. No. 28,316 Claims priority, application Netherlands Aug. 14, 1959 12 Claims. (Cl. 313-213) My invention relates to a glow discharge tube. More particularly, the invention relates to a voltage reference tube in which a visible layer of the cathode material is present on the wall surrounding the discharge path.

This application is a continuation-in-part of my application Serial No. 797,171, filed March 4, 1959.

Gaseous glow discharge tubes of the aforesaid type are known for their favorable properties, particularly with regard to their constant burning and striking voltages. Such tubes are often used in circuits imposing the requirements of a very stable voltage, and as triggering tubes which are required to satisfy very narrow tolerances.

One of the requirements for such tubes is that of cathode materials having a melting point higher than 1400 C., among which molybdenum is preferred because of the ease with which the coating on the wall of the tube may be obtained by atomization of the cathode surface, and because of the reproducibility of the properties of the tube. However, voltage stabilizer tubes of the aforesaid type may exhibit diiferences in operating voltage of 2 to 3%.

The principal object of my invention is to provide a gaseous glow discharge tube which exhibits smaller differences in operating voltage and which are thus more readily interchangeable.

In accordance with the invention, the cathode of a glowdischange tube, of which the wall is coated with cathode material, consists of a plate of monocrystalline-germanium or -silicon. The diiferences in such cathodes are less than in the polycrystalline cathodes, and their constancy is distinctly better.

In a preferred embodiment of my invention, the cathode consists of a germanium-monocrystalline plate, the surface of which is parallel to the (1, 1, 1)-crystal planes.

In another embodiment of the invention, a monocrystalline-silicon plate-shaped cathode is employed, since it offers particular advantages with respect to germanium in that the cathode temperature elfect, which occurs with these materials, is about 20 times less with silicon than with germanium. Thus, in the case of variation in the temperature of the discharge tube, not only a variation in burning voltage occurs, which is attributable to the modified distribution of density and which is balanced within several seconds, but also a gradual decline in burning voltage occurs within a few hours up to a final value which is presumably attributable to rare-gas ions which have been shot in the cathode material.

The results for germanium apply both to germanium of perfect purity, and hence of exclusively intrinsic conductivity, and to germanium which has been made nor p-conducting by means of additions of impurities. Because of its higher resistance, silicon is only serviceable in the nor p-conductive state.

The invention will now be described with reference to the drawing which shows a gaseous glow discharge tube according to the invention.

In the figure, reference numeral 1 designates the glass base of the tube with supply conductors 2; 3 designates a quartz cylinder bearing on the base; 4 designates the oathode plate which is pressed on cylinder 3 by means of two rigid molybdenum springs 5, welded to lead-through pins. The main anode comprises a molybdenum plate 6, and the auxiliary anode a molybdenum block 7. Apertures 8 are provided on the walls of the quartz cylinder which is provided with a layer 10 of visible thickness and of the same material as the cathode on the surfaces surrounding the discharge. The bulb of the tube is designated 9. With a gas filling of neon at a pressure of 40 mms. of mercury, burning voltages were obtained, as specified in the table below:

Cathode burning voltages Crystal Directions Cathode Material Polycrystalline 1,0,0 1,1,0 1,1,1

Ge 132. 0 129. 8 131.0 Si 134. 5 134. 0 133. 4 137 Crystal directions While I have thus described my invention with specific embodiments and applications thereof, I do not wish to be limited thereto since other modifications will be readily apparent to those skilled in the art. The invention is defined in the appended claims which should be construed as broadly as permissible in view of the prior art.

What I claim is:

1. A gaseous glow discharge tube comprising an envelope, a gaseous medium within said envelope, anode and cathode electrodes within said envelope and defining a discharge path therebetween, said cathode being plateshaped and consisting of a monocrystal of an element se lected from the group consisting of germanium and silicon, and a coating of the same material as the cathode of visible thickness on the portion of the inner wall of the envelope exposed to the discharge.

2. A gaseous glow discharge tube comprising an envelope, a gaseous medium within said envelope, anode and cathode electrodes within said envelope and defining a discharge path therebetween, said cathode being plateshaped and consisting of a monocrystal of germanium, and a coating of germanium of visible thickness on the portion of the envelope exposed to the discharge.

3. A gaseous glow discharge tube comprising an en velope, a gaseous medium within said envelope, anode and cathode electrodes within said envelope and defining a discharge path therebetween, said cathode being plateshaped and consisting of a monocrystal of silicon, and a coating of silicon of visible thickness on the portion of the envelope exposed to the discharge.

4. A gaseous glow discharge tube as claimed in claim 2, in which the surface of the cathode is parallel to the (l, 1, (D-crystal planes.

5. A gaseous glow discharge tube as claimed in claim 2, in which the surface of the cathode is parallel to the (1, 1, 1)-crystal planes.

6. A gaseous glow discharge tube as claimed in claim 3, 0

crystal plate cathode the surface of which is parallel to the (1, 1, 1)-crystal planes within said envelope, :1 hollow support for said cathode defining a glow discharge space, an anode within said glow discharge space, and a coating of germanium of visible thickness on the inner wall of said support.

12. A glow discharge tube as claimed in claim 11 in which the cathode support is quartz.

No references cited. 

